1. Field of the Invention
The present invention is directed generally to a casting device and method, and more specifically to a dental casting device for creating a dental prosthesis with efficient metal recovery and harmful-vapor minimization.
2. Description of Related Art
It is well-known that high-purity precious metals are used in the formation of prosthetic dental pieces. Traditionally, a mold of the desired dental impression was inserted into a mold along with an amount of the precious metal to be cast into a crucible. The precious metal was subjected to high temperatures allowing the metal to melt while the centrifugal force imparted thereon forced it into the mold, thereby creating the dental piece.
Such a centrifugal casting machine was required to rotate the molten metal and the mold at a high angular velocity to adequately fill the mold with the molten metal. This was typically accomplished by rotating an arm holding the metal and the mold within a cylindrical container such as a drum. The walls of the drum acted as a safety measure to minimize the number of articles cast outside of the drum possibly a bystander during rotation of the mold and the metal. However, for convenience, the assembly comprising the arm that was rotated was elevated above the bottom of the drum at a convenient working height for the operator. This left a significant void between the rotational arm of the casting machine and the bottom of the drum.
During a typical casting operation, it was common for at least a portion of the precious metal to miss the mold due to the high angular velocity at which the arm assembly was rotating. These trace amounts, typically no more than fractions of an ounce, are cooled while they are cast in a radially-outward direction towards the wall of the drum, and are typically at least partially solidified by the time they reach that wall. As such, upon impacting the sidewall of the drum, the particular precious metal falls through the void between the bottom of the drum and the rotational arm and eventually comes to rest at the bottom of the drum. For precious metals such as gold, platinum, and titanium that are expensive, the loss of even trace amounts of these metals over a prolonged period of time can amount to significant losses to the proprietor.
In addition to problems associated with costs due to lost metals, the casting environment also poses a risk to the health of an operator standing close to the machine. The high temperatures required to melt the precious metals to be used in the dental prosthesis tend to vaporize potentially toxic impurities found on the crucible used to melt the metal, the mold in which the dental prosthesis is cast, and other materials involved in the casting process. Vaporization of these potentially toxic materials requires safety measures to minimize the amount of toxic materials inhaled by the operator.
Yet other environmental hazards exist in the dental casting process. For instance, the high angular velocity at which the arm supporting the mold must rotate poses a threat to limbs of the operator coming into contact with the arm. Further, conventional casting machines often require the operator to manually wind the arm in one direction to load a spring that recoils to rotate the arm in the opposite direction at a high angular velocity. Again, this requires the operator to make physical contact with the arm immediately prior to the arm reaching a high angular velocity.
Accordingly, there is a need in the art for a dental casting machine that makes efficient use of precious metals, and minimizes potentially harmful environmental hazards to which an operator is exposed.